In recent years, new microfabrication technologies have been developed along with enhancement of integration and higher performance of a large scale integrated circuit (hereinafter, referred to as “LSI”). A chemical mechanical polishing (hereinafter, referred to as “CMP”) is one of new microfabrication technologies and is frequently used in a manufacturing process of LSI. In particular, CMP is used in surface flattening of an insulating body in a step of forming a multilayer wiring structure, formation of a metal plug, and formation of an embedded pattern (embedded metal wiring).
In addition, in recent years, to achieve higher performance of LSI, use of copper, copper alloys, copper oxides, and oxides of copper alloys (hereinafter, collectively referred to as “copper type metal”) is tried as a wiring material. However, the copper type metal is difficult to be microfabricated with a dry etching method, which is, in the past, frequently used in formation of aluminum alloy wiring. Then, so-called the Damascene process is mainly used of which the copper type metal is deposited for embedding into trench portions formed in advance on an insulating body and the copper type metal in the area other than the trench portions is then removed by CMP to form an embedded pattern.
A general CMP process for metal is a process in which a polishing pad is attached to a circular polishing wheel (platen) and the surface of the polishing pad is soaked with a metal polishing liquid followed by pressing the surface of metal formed on a substrate under the given pressure (hereinafter, referred to as “polishing pressure”) from the backside of the substrate to the polishing pad while rotating the polishing wheel, thereby removing the metal in the convex parts by mechanical friction between the polishing liquid and the convex parts of the metal.
A metal polishing liquid used in CMP generally contains an oxidizing agent and solid abrasive grains. It is presumed that addition of a metal-dissolving component (metal solubilizer, metal oxide solubilizer, etching agent, and the like) is effective to increase a polishing rate in CMP. However, when the oxide layer of the metal surface in the concave parts is also dissolved (hereinafter, referred to as “etching”) and the metal surface is exposed, the metal surface is further oxidized by oxidizing agent. Repetition of this process causes further etching of the metal in the concave parts, thereby causing potential reduction of the planarization effects. To prevent the progress of etching, a protective film-forming agent is further added.
Such addition of the metal solubilizer and the protective film-forming agent promotes the effects of chemical reaction for increasing the polishing velocity in CMP (hereinafter, sometime referred to as a “polishing rate”) as well as for reducing a damage of the metal surface subjected to CMP. At present, in addition to the metal solubilizer and the protective film-forming agent, use of various substances such as a polymer electrolyte, phosphonic acid, and the like is evaluated as an additive, leading to yield a relatively high polishing rate and a low etching rate. These technologies are disclosed, for example, in Patent Literatures 1 and 2.
As a polishing liquid for polishing copper type metal, a metal solubilizer containing an oxidizing agent, a metal dissolving agent, a first protective film-forming agent, a second film-forming agent different from the first protective film-forming agent, and water is known, in which the first protective film-forming agent described above is a compound to form a protective film on the metal surface by physical absorption and/or chemical bonding and the second protective film-forming agent described above is a compound to assist the first protective film-forming agent to form the protective film (refer to Patent Literature 3). More specifically, a metal polishing liquid is disclosed of which the first protective film-forming agent described above is at least one type selected from benzotriazole and its derivatives and the second protective film-forming agent described above is at least one type selected from polyacrylic acid, polymethacrylic acid, polyamic acid, ammonium polyacrylate, ammonium polymethacrylate, ammonium polyamate, and polyacrylamide. It is presumed that such a metal polishing liquid can polish the copper type metal at good polishing rates while preventing the copper type metal from etching.
In addition, as a similar polishing liquid, a metal polishing liquid containing a metal solubilizer, a metal corrosion inhibitor (protective film-forming agent), polyacrylic acid type polymer, and water, to which a large amount (12 to 30% by mass) of hydrogen peroxide is added relative to the mass of the metal polishing liquid is known (refer to Patent Literature 4). It is presumed that use of such a polishing liquid can generate good polishing rates for a copper type metal even with a low polishing pressure so that a polished surface excellent in flatness can be obtained.